GB864048A - A method and means for hardening a surface of an article by electrical induction heating and quenching - Google Patents

Abstract

864,048. Heat treating. DELAPENA & SON Ltd. June 20, 1957 [June 21, 1956]. No. 19281/56. Class 72 [Also in Group XI] A method of hardening a reentrant surface of an article by induction heating and quenching comprises the steps of immersing the re-entrant surface and the heating or work face of an inductor shaped substantially to fit the contour of the re-entrant surface in a liquid cooling medium and whilst maintaining the inductor and the re-entrant surface in closely spaced relation and submerged in the liquid cooling medium feeding electrical current to the inductor and effecting relative movement between the inductor and article to cause the re-entrant surface of the article to be traversed longitudinally and heated by the inductor and immediately quenched by the liquid cooling medium in which it is immersed. The machine shown is for hardening the teeth of gear wheels. Inductor and mounting. An inductor 26 is detachably secured to the under surface of a transformer unit 27 which supplies high frequency current to the inductor and which depends from the end portion 25a of a carrying assembly 25. The assembly is slidable and rotatable on a bar 23, movement along the bar being effected by a lead screw 43 co-operating with a halfnut 44 and rotated by power means 62 or by a hand wheel 43a. The end portion 25a of the assembly is attached to the remainder by vertical slides, and raising or lowering of the end portion and the inductor enables gear wheels of different diameters to be hardened. To enable the inductor and guide means 65 to be swung about a vertical axis to conform to the helix angle of a helical gearwheel, the portion 25a of the assembly 25 is supported on curved guides 77, Fig. 4, fine adjustment being provided by a screw and nut mechanism 78. Mounting for gearwheels. A surface plate 31 carried on a support 32 may be raised or lowered and has projecting arms 33 provided with recessed blocks 34 for receiving a shaft 36 on which a gearwheel 30 is mounted. In a modification, for use with bevel gearwheels, Fig. 10, a surface plate 31a is mounted on a pivot 79 provided in a block 80 vertically slidable in a slot 81 formed in a support 32a. A screw shaft 82 rotatable by a handle operated shaft 83 engages in the block which is provided with a nut and bolt 85 for securing the plate 31a to the support 32a. Further securing means 87 are provided and a screw device 90 permits accurate angular adjustment of the plate 31a. Gearwheel positioning and indexing. Positioning of the tooth space to be traversed relatively to the inductor is effected by the guide means 65 adjustably fixed to the carrying assembly 25. The rounded surfaces of two balls 66 engage with a tooth space closely adjacent to the inductor, downward pressure on the balls by the assembly 25 being reduced by a counterweight 72. For moving each tooth space seequentially into register with the inductor, an indexing element is given timed reciprocating movement by a link mechanism 60 and a power-driven cam 61. Quenching. A tank 46 for the cooling liquid may be raised or lowered by means of an electric motor, stops being provided for controlling the vertical travel of the tank in conformity with the diameter of the gearwheels being processed. Auxiliary cooling means comprises nozzles 52 arranged one on each side of the inductor and adjustably supported from the upper end thereof. In place of the tank 46, an arrangement for containing the cooling liquid may be built around the gearwheel. Operation. The tank is raised until the level 47 of the cooling liquid lies between the upper and lower ends of the inductor. The heating step is performed by effecting horizontal traversing movement of the carrying assembly 25 by rotation of the lead screw 43, the inductor traversing the tooth space of the gearwheel from end to end. The inductor is guided into a tooth space and as soon as the inductor enters the space, each quenching jet is directed on to the tips or top lands of the teeth bounding the tooth space and down the adjacent side surfaces of such teeth. The traversing movement of the assembly 25 brings into sequential operation means for automatically varying the order of the current fed to the inductor and/or the speed at which the traversing movement is effected to enable the desired heat pattern to be obtained on the teeth. Switching on and off of the current to the inductor is also effected by movement of the assembly 25. In the case of plain gear wheels having no shoulder adjacent to the teeth, heating is carried out in both directions of traverse of the inductor. With shouldered gearwheels, the machine is set so that heating is effected by movement of the inductor in one direction only.